Log sycl-ls error messages related to adapter loading (#17490)

Changes:
* change the log level to "error" for all errors related to adapter
dependencies during UR adapter loading
* enable the printing of UR adapter errors in sycl-ls from
platform::get_platforms() using environment variables

With this PR, there will be no changes for the user in the default
scenario where some adapters exist and some are missing (a missing
adapter is not considered an error). In cases where a dependency is
missing, the following example message will be displayed:

```
<LOADER>[ERROR]: failed to load adapter 'libur_adapter_level_zero.so.0' with error: libumf.so.0: cannot open shared object file: No such file or directory
```

Here is the message for missing symbols (a case where a dependency is
not compatible with the rest of the libraries):

```
<LOADER>[ERROR]: failed to load adapter 'libur_adapter_level_zero.so.0' with error: /home/rrudnick/llvm/build/lib/libumf.so.0: version `UMF_0.10' not found (required by /home/rrudnick/llvm/build/lib/libur_adapter_level_zero.so.0)
```

Author: bratpiorka

source/common/linux/ur_lib_loader.cpp

@@ -50,9 +50,20 @@ LibLoader::loadAdapterLibrary(const char *name) {
 #endif
   HMODULE handle = dlopen(name, mode);
   if (!handle) {
-    char *err = dlerror();
-    logger::info("failed to load adapter '{}' with error: {}", name,
-                 err ? err : "unknown error");
+    const char *err = dlerror();
+
+    // Check if the error string does not contain the adapter name or if it
+    // contains a "required by" (missing symbol) message.
+    if (err &&
+        (strstr(err, name) == NULL || strstr(err, "required by") != NULL)) {
+      // If the adapter cannot be loaded due to missing dependencies or any
+      // other related error, it is considered as an error.
+      logger::error("failed to load adapter '{}' with error: {}", name, err);
+    } else {
+      // Simply having the adapter library missing isn't an error.
+      logger::info("failed to load adapter '{}' with error: {}", name,
+                   err ? err : "unknown error");
+    }
   } else {
 #if defined(ADD_FULL_PATH_LOG)
     struct link_map *dlinfo_map;